Electronic musical instrument



June 27, 1967 H. PETERSON 3,328,507

ELECTRON I C MUS I CAL IN STRUMENT Filed June 28, 1963 2 Sheets-Sheet l 34 V 1- /0 42 -3 Z6 4 l L {4 Z2 32 3a 61 12 J8 7 1 66 flPalazsorz June 27, 1967 R. H. PETERSON 3,328,507

ELECTRONIC MUSICAL INSTRUMENT Filed June 28, 1963 2 Sheets-Sheet ZONE-I ZONE-2 ZONE-3 /Z& 122 $9 s l y 42 .1 J?! /9 a J14 ,z

/ Jazz/em 42 %7ezfaserc United States Patent M 3,328,507 ELECTRONIC MUSICAL INSTRUMENT Richard H. Peterson, 10108 Hamew Road,

. Oak Lawn, Ill. 60453 Filed June 28, 1963, Ser. No. 291,377 3 Claims. (Cl. 841.26)

My invention relates to electronic organs and similar electrical musical instruments, and includes among its objects and advantages, a greatly improved key switch assembly having gradual resistance characteristics. With respect to the problem of scaling, it also 'brings within reasonable cost limits, a gradual and continuously progressive scaling throughout the range of the instrument.

In the accompanying drawings:

FIGURE 1 is a partial side elevation of the connections for one key in a key switch assembly;

FIGURE 2 is a greatly enlarged diagrammatic view of a variable resistance switch contact according to the invention;

FIGURE 3 is a view similar to FIGURE 2 indicating a different type of variable resistance contact;

FIGURE 4 is a similar view indicating still another form of the invention;

tion.

In the embodiment selected to illustrate the invention, I have indicated a conventional playing key forming part of a'conventional keyboard. Counter-clockwise rotation of the key is limited by the conventional adjustable stop 12 mounted in the fixed rail 14, and the pivot for the key is at 16 on a fixed rail 18. The remote end of the key has 'a contact portion 20 adapted to engage the lower end of a riser 22. Suitable means are provided forguiding the riser. I have illustrated a support 24 having guide plates 26 and 28 apertured to receive the riser 22 and guide its movement. Spaced 'behind'the riser is a support 30 providing fastening means for the ends of a plurality of close-wound helical springs of which three are illustrated at 32, 34, and 36. It will be borne in mind that there are nite number of contact members may be associated with each riser.

I have indicated a signal source 38 of the frequency "corresponding to the particular key 10 illustrated, for

instance, C The signal from the source 38 passes through the conventional anti-robbing resistor 40 to the contact member 32. 7

Close above the contact member 32, I have indicated a multiplicity of keys 10, each with its riser and associated helical spring contact members, and that an indefia' signal-collecting bus-bar. The electrically conductive element 42 constitutes the collecting bus proper, but it is supported on a rigid support extending the length of the instrument. The support illustrated includes a structural support 44 and a non-conductive lower plate, or strip of flexible plastic, 46 affixed to it. Thelower surface of the strip 46 is curved arcuately upward and the bus proper 42 is aifixed tothe strip 46. It will be apparent on reference to FIGURES 1 and 2 that an upward displacement of the riser 22 will move the adjacent end of the contact member 32 upward until the contact member occupies the position of the dotted line 48 in FIGURE r 3,328,507 Patented June 27, 1967 2. As this movement takes place, there will be temporary transverse resistance from the first contact of the member 32 with the edge of a high resistance zone 2 extending from end to end of the bus 42. This temporary transverse resistance may be of several megohms or tens of megohms. The final position at 48 will involve relatively negligible resistance between the conductor 32 and its contact area with the low-resistance zone 1, which extends to the edge of the bus. It is mechanically convenient to let the support 46 extend a little beyond the rear edge of zone 2 to form a non-conductive heel zone 3.

Referring now to FIGURE 6, I have diagrammatically indicated eight of the oscillators for a clavier including 61 notes. The bus 42 extends past all of them and engages the contact member 32 of each of them whenever the corresponding key is depressed.

It will be apparent that the path of the signal from the source 38 is through its anti-robbing resistor 40, than across as much transverse resistance of the zone 2 as the contact position of the member 32 determines, indicated diagrammatically in FIGURE 6 as R while the antirobbing resistor is designated R and the internal resistance of the generator R The next resistance is indicated as R; and is the resistance of that portion of the bus 42 between the contact for the particular note and the output terminal, or tap, 50 .at the left end of the bus. From there the signal is afforded two paths, one through the amplifier input resistor R and the other through a resistor 76 and conductor 52 and a stop switch 54 and filter 51 to the loud speaker 56. When the stop switch 54 is closed and one or more keys on the clavier are depressed, all the corresponding oscillators will deliver signal and the superimposed signals will be transduced into acoustical vibraof the anti-robbing resistor, designated R plus the momentary transverse resistance of zone 2 from contact point to zone 1 depending on the momentary position of the contact member and designated R plus the resistance of as much of the bus 42 as extends from tap 50 to the contact 32 for that note, designated R plus the amplifier input resistance R as expressed in the following equation:

R output input X m Assuming that R is negligible, which is a practical assumption, one specific example of the remaining resistances may be of the following order of magnitude:

R 3 0,000 ohms;

R variable from 5 or 1 megohms down to zero, as the key moves to completely depressed conditions;

R -oonstant for each note but different for each of the different notes depending on the position ofthat note with respect to the tap 50;

R 5,000 ohms.

' Many acoustical instruments have characteristic variations in loudness and tone quality, which the musically trained ear has learned to expect and admire. In general,

with the same signal amplitude from all the oscillators of an electronic organ, the acoustic amplitude is too low at the low end of the scale and is too high near the top of the scale. Also, other anomalous variations in loudness at different frequencies are introduced by certain types of filters and other signal-processing instrumentalitie's.

It is known to compensate for this by subdividing a collecting bus into a plurality of segments, with a resistance between each segment and the next. It will be apparent that the bus 42 can accomplish this same function with as many steps as there are notes on the instrument, which steps are not noticeable to the user because they duplicate the small progressive steps of the corresponding acoustical instrument. It is quite easy to make the resistance of the bus 42 so low that it is negligible and no progressive change in signal amplitude at the tap 5t) occurs. But any desired degree of progressively reduced amplitude, or scaling, can be secured by giving the right longitudinal resistance characteristics to the bus. Then when the player plays a number of different notes simultaneously, each of the signals will have its relative amplitude sea-led to precisely the right degree to duplicate the esthetic effect desired by the designer of the instrument.

It will be obvious that the direction of the scaling, and the points of maximum amplitude with respect to which the scaling is orientated, may be varied in many ways to meet desired conditions. For instance, at the right end of the collecting bus 42 in FIGURE 6, I provide a second connection for with-drawing signal sealed in the opposite direction. Beyond the tap 60, at the right end of the bus 42, I provide the conventional amplifier input resistor 62, and the utilized signal passes through resistor 63, filter 64, stop switch 66 and conductor 68 to the amplifier 55 and loud speaker 56.

Similarly, from tap 69, on the bus 42, adjacent the connection for receiving frequency C signal in conductor 70 is retained by amplifier input resistor 73, and passes through resistor 74 and filter 75 to stop switch 71 and conductor v68. In the signal delivered from filter 75, frequency C will be emphasized, and a signal of either higher or lower frequency will be scaled in proportion to the bus resistance between the tap 69 and the point where the signal of different frequency is received by bus 42.

The bus-bar element proper 42 may by a thin film of carbonaceous material deposited on the surface of the non-conductive support 46. This film, as indicated in FIG- URES 7 and 8, is of maximum conductivity in a first zone 1, last engaged by the contact element 32 during the closing of the switch.

At any instant, the attenuation of any signal reaching the bus, is due to the resistance between zone 1 and the contact of the playing switch member 32 nearest zone '1.

Loudness is a geometrical function, measured in decibels. The human ear is capable of response to sound varying from faint whispers to ear-splitting concussions and roars. The range desired in musical performances includes this entire range, except for magnitudes where the sensation becomes painful to the ear.

To secure this unusually wide spectrum of amplitudes conveniently, the preferred film 42 is a suspension of very fine carbon particles suspended in a matrix of a suitable resin, such as epoxy resin. This can be sprayed on the supporting sheet 46 with a conventional air gun, in very fine droplets. Variation in the amount of material present proceeding transversely across the zones, can be obtained in a variety of ways.

One convenient way is by making the amount applied on each pass of the air gun a minor fraction of the total carried in zone 1, and screening increasing portions of zone 2 during successive passes. This can be carried to any desired extent, and in present practice the desired ratio is about 25 to 1. In other words, practically all of zone 1 receives 25 passes, and high resistance edge of zone 2 receives only 1. Proceding transversely across zone 2, the number of passes or layers of conductive material increases from 1 to 25, in a plurality of pro-determined steps.

At the thin edge of zone 2, there results a narrow area where the tiny globules projected by the spray gun have made isolated gobs or blots on the support, much terms of resistance, might as well be naked, but it merges into an area where chains of the tiny blots have edge coalescence, and such chains then become continuous and lead in devious paths into the thicker material beyond.

The resistance of such an individual chain depends, first, on the specific resistance of the material of each blot, and second, on the extent of edge overlap between one blot and the next. This open network of closed chains, has a random configuration analogous to the fine roots at the ends of the root structure ofa tree. The network gets to be of smallermesh and individual chains come to cross over each other more and more frequently. The open network affords cross connections that afford a large number of parallel current paths, merging and intersecting at intervals, and this may multiply the over-all conductivity of the film by several orders of magnitude.

Then the openings between the chains begin to occupy only a minor fraction of the total area, and that condition adds more decibels. Then the openings are completely absent and the crossings begin to pile up two and three deep, adding several more decibels. Inside the individual blots at the high-resistance edge of zone 2, and inside the entirety of zone 1, the specific resistance of the three-dimensional continuum, depends, (1) on the conductivity of the conductive particles, (2) on the concentration of the particles in the continuum, and (3) on the electric properties of the matrix, especially where a filmof matrix between two adjacent particles is at or near the point of penetration by the conductive particles.

It will be obvious that the specific conductive or dielectric properties of the particles and of the matrix, as well as the concentration of the particles in the matrix and the size of the particles, represent. four factors, each of which can be varied over a substantial range. In present practice, using finely powdered carbon and epoxy resin, an adequate range for music is secured without varying any ofthe factors last mentioned, within the different areas of the completed unit.

It is diffic-ult to portray in a drawing the smooth graduation of the conductivity across zone 2 of the collecting bus. In FIGURE 7, I have tried to make a showing that will be convenient for search purposes, by using a heavy stipple for zone 1, and a stipple that is darkest next zone 1 and fades out to nothing at all at the opposite edge of zone 2. To supplement this, FIGURE 8 is a diagram in which conductivity is measured on the vertical axis and linear extent across the bus is along the horizontal axis.

It is convenient to discuss'the structure in words by referring to three different zones, including the heel 3, but in the actual structure there need not be any lines of demarcation anywhere. At least the lower half of the conductivity curve 112 for zone 2 in FIGURE 8 'approaches the zero value of the heel 3 in a close approximation to a logarithmic decrement curve asymptotic to the horizontal zero line of the heel 3. A substantial fraction next the plateau 110, representing the maximum conductivity throughout zone 1, is of reversed curvature and asymptotic to the plateau.

Referring now to FIGURES l and 6, the contact element 34 is associated with a bus 78 of the same type as bus 42 and the contact member 36 is associated with a bus 80, which is an ordinary metallic conductor and will not have the variable resistance attack characteristic of the buses 42 and 78. In some organs some of the associated elements do not require the collecting bus 42.

In FIGURES 1 and 6, I have indicated several sections of a second bus 78. The left end of the bus has an am plifier input resistor 81 and a balancing resistor 82 leading to a stop switch 84. When the key 10 is depressed, bus 78 receives signal through a conductor 86 from oscillator C and the upper end of bus 78 is at 88, where the contact member 32 is associated with key C and receives signal through conductor 90 from oscillator C Thus, with stops 54 and 84 both closed, the depression of any key up to C will deliver signal from the signal source having the same nominal frequency as the key, to bus 42. Simultaneously, signal will be delivered to bus 78 from a source an octave higher, commonly called the 4 foot stop. It will be obvious that the longitudinal resistance properties of bus 78 need not be the same as bus 42 and that by providing a multiplicity of such buses, the riser associated with each key may function for simultaneous delivery of such other frequencies as may be desired, to harmonize with the lowest frequency controlled by that riser. Also, the scaling of the octave bus 78 need not be the same as the scaling for the lower frequency bus 42.

Referring now to FIGURE 3, I have indicated an alternative support for bus 42 in which the bus itself lies all in one plane and the contact element is a flexible metal strip anchored at 92 and having an arcuate end portion 94 and a short projection at 96 to receive the upward force to flex it up against the bus.

In FIGURE 4, I have indicated a modified contact element anchored at 98 and comprising a relatively flexible portion 100 and an arcuate end portion 102 stifiened by a rib 104. When an upward displacement is imposed on the tip 106, the greater rigidity of the arcuate portion will cause it to rock into the closed position, with the more flexible portion 100 bent down into an upwardly concave arc. In this construction the shortening of the flexible metal portion 100 causes the stiff arcuate portion to have a slight sliding motion. This tends to secure smoother and more dependable contact.

It is noted that flexure of the strip 46 into the upwardly concave configuration of FIGURE 2, is necessary only to enable the flexible helix 32 to change its contact area with the bus 42 by curving during upward movement of the riser 22. In FIGURES 3 and 4 it is the other contact element which flexes to produce the change of the contact area, and the rigid support 44, and the alfixed sheet 46 have plane surfaces. In either case, the support 46 is merely a thin flexible plastic strip, or ribbon.

Referring now to FIGURES 9 and 10, the insulating support 114 corresponds to the support 46 of FIGURES 2 and 3 and its bottom coating 42 corresponds to that of the same figures. But the coating in FIGURES 9 and 10 has been separated by scraping it away along narrow parellel lines 116 transverse to the longitudinal direction of the support. Each of the separate conductive areas thus defined can function transversely in the same way as if there had been no such separation.

To provide separate buses for the two sets of associated key switches, a metallic film 122 on the upper surface of the sheet 114 is simply separated longitudinally by scraping it way at 126. At least the separated portion remote from the edge of the film 42, is connected by forming a hole 120 through the sheet 114. During the application of the films, either or both of the films may flow more or less into the hole 120 and coat its side wall, or fill it, enough to establish good electrical connection through the sheet 114.

In FIGURE 10, I have illustrated both films connected through the sheet 114 in this way.

In FIGURE 11, the bus next to the edge is connected by letting one of the films run over the edge of the sheet at 128, but only where the bottom carbon area has no electric connections through the support 114.

It will be obvious that such a multiple connection is not limited to two areas, but might extend to any reasonable number. The practical limit is only a matter of enough width in the metal bus to form the desired number of separate strips, and making the conductive areas of the resistance film narrow enough to come within the dimensions of the keyboard. In such a multiple connection, the scaling resistance, if any, is naturally put in the bus, and the individual areas of the transverse resistance film do no scaling. The multiple connections may obviously be used either to sound a plurality of harmonically related frequencies, or to have adjacent frequencies in separate channels.

It is noted that the riser 22 of this application performs the switching functions of the lifters 92 of U8. Patent 3,027,418, issued to me Mar. 27, 1962. Further, the switch ing function of the entire key switch assembly 10 of that patent is replaced by the key switch assembly of FIGURE 1 of this application. The simple, conventional, output circuits controlled by switches 54, 66, 71 and 74 (see FIG- URE 6 of this application) replace the entirety of the additional structure illustrated in FIGURE 2 of the patent. But the simple structure of this application also performs a wide variety of assorted scaling functions, and an attack envelope determining function for each key switch. None of these additional functions are performed at all by the key switch assembly of my earlier patent.

Others may readily adapt the invention for use under various conditions of service by employing one or more of the novel features disclosed, or equivalents thereof. As at present advised with respect to the apparent scope of my invention, I desire to claim the following subject matter:

'1. In an electronic musical instrument, in combination: a manual of playing keys corresponding to the notes of the musical scale; a support extending longitudinally parallel to said manual; a strip of flexible non-conductive material detachably affixed to said support; and a conductive film adhering to the face of said strip remote from said support; said film having a longitudinal zone of relatively high conductivity along one, outer edge; said film having a longitudinal area of variable conductivity parallel to and merging with said high-conductivity zone, remote from its outer edge; and individual contact elements, each connected to be moved by depression of its individual playing key to make contact progressively in a transverse direction across said variable resistance area toward said high-conductivity zone during depression of the key and back in the opposite direction when the key is released.

2. A combination according to claim 1 in which said variable conductivity area is of decreasing conductivity transversely of said film; the conductivity decreasing in predetermined degrees as the distance from said high conductivity zone increases.

3. A combination according to claim 1 in which the high conductivity zone of said film has longitudinal resistance between each note and the next; whereby taps connected to said zone at any point along its length will receive signal scaled in favor of the notes nearest the tap.

References Cited UNITED STATES PATENTS 1,855,155 4/1932 Sampson 343-908 X 2,215,124 9/1940 Kock et al. 33869 2,215,708 9/ 1940 Miessner 84122 2,458,178 1/1949 Langer 841.17 2,683,673 7/1954 Silversher 338- 211 X 2,874,286 2/1959' Bode 841.19 2,959,693 10/1960 Meyer 841.01 X 6,041,568 6/1962 Bissonette et al. 338-69 3,134,689 5/1964 Pritiken 338308 X 3,152,840 10/ 1964 Lin 30788.5 3,197,335 7/1965 Leszynski 338308 X ARTHUR GAUSS, Primary Examiner. DAVID J. GALVIN, Examiner. D. D. FORRER, Assistant Examiner. 

1. IN AN ELECTRONIC MUSICAL INSTRUMENT, IN COMBINATION: A MANUAL OF PLAYING KEYS CORRESPONDING TO THE NOTES OF THE MUSICAL SCALE; A SUPPORT EXTENDING LONGITUDINALLY PARALLEL TO SAID MANUAL; A STRIP OF FLEXIBLE NON-CONDUCTIVE MATERIAL DETACHABLY AFFIXED TO SAID SUPPORT; AND A CONDUCTIVE FILM ADHERING TO THE FACE OF SAID STRIP REMOTE FROM SAID SUPPORT; SAID FILM HAVING A LONGITUDINAL ZONE OF RELATIVELY HIGH CONDUCTIVITY ALONG ONE, OUTER EDGE; SAID FILM HAVING A LONGITUDINAL AREA OF VARIABLE CONDUCTIVITY PARALLEL TO AND MERGING WITH SAID HIGH-CONDUCTIVITY ZONE, REMOTE FROM ITS OUTER EDGE; AND INDIVIDUAL CONTACT ELEMENTS, EACH CONNECTED TO BE MOVED BY DEPRESSION OF ITS INDIVIDUAL PLAYING KEY TO MAKE CONTACT PROGRESSIVELY IN A TRANSVERSE DIRECTION ACROSS SAID VARIABLE RESISTANCE AREA TOWARD SAID HIGH-CONDUCTIVITY ZONE DURING DEPRESSION OF THE KEY AND BACK IN THE OPPOSITE DIRECTION WHEN THE KEY IS RELEASED. 